fix(@gms/gms-plugin-billexpand): 写入主表模板字符串若字段为空不应显示undefined

develop/@gms/gms-plugin-billexpand/src/formula/ApplyTemplateString.js

@@ -57,6 +57,7 @@ export default {
           for (let i = 1; i < value.length; ++i) {
             ans = ans[value[i]]
           }
+          if (!ans) ans = ''
           templateString = templateString.replace(str, ans)
         })
         return templateString